CN110841623A - Cerium-zirconium composite oxide with stable high-temperature structure and preparation method thereof - Google Patents
Cerium-zirconium composite oxide with stable high-temperature structure and preparation method thereof Download PDFInfo
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Abstract
The invention provides a preparation method of a cerium-zirconium composite oxide with stable high-temperature structure, which comprises the following steps: dissolving and mixing a cerium source, a zirconium source and at least one rare earth metal source except cerium to obtain an acidic mixed solution, adjusting the pH of the acidic mixed solution to 3-6, carrying out coprecipitation reaction with an alkaline precipitator, carrying out hydrothermal reaction, and carrying out high-temperature heat treatment on the obtained product to obtain the cerium-based cerium-doped cerium oxide. The preparation method of the cerium-zirconium composite oxide provided by the invention has the advantages of simple process, lower cost and easy industrialization, and the cerium-zirconium composite oxide prepared by the preparation method has better low-temperature catalytic activity, obvious high-temperature structural stability and high utilization rate of noble metals, and is suitable for industrial production.
Description
Technical Field
The invention relates to the technical field of tail gas purification and catalysis, in particular to a cerium-zirconium composite oxide with a stable high-temperature structure and a preparation method thereof.
Background
The cerium-zirconium composite oxide is an important component of a three-way catalyst, the performance of the cerium-zirconium composite oxide determines the purification effect of automobile exhaust, and with the successive execution of national VI standards, the synthesis of the cerium-zirconium composite oxide meeting the standards becomes the key direction of the current research.
CeO2Sintering easily occurs at high temperature, the particles grow large, the specific surface area is reduced, thereby reducing the oxygen storage capacity and leading to catalyst deactivation, ZrO2The introduction of (A) can effectively improve CeO2High temperature thermal stability and oxygen storage capacity. Zr + enters CeO2In the crystal lattice, the Zr + radius is less than that of Ce4+Causing distortion of cerium oxide crystal lattice and generation of defects, enhancing the fluidity of crystal lattice oxygen, and slowing down the growth of cerium oxide crystal grains at high temperature. Therefore, the high-temperature structural stability and the reduction performance of the ceria-zirconia solid solution become major factors affecting the activity of the three-way catalyst.
The existing preparation methods of the cerium-zirconium solid solution comprise a sol-gel method, a coprecipitation method, a hydrothermal method and the like. Among them, the sol-gel method is one of the most commonly used methods for preparing functional materials of oxide type, and the oxide prepared by the method has a pore structure interconnected in three-dimensional directions. The size of the pore diameter and the direction of the pore can be regulated and controlled by a certain means, but the preparation conditions are strict, and large-scale application is not easy to realize. The coprecipitation method is one of the commonly used methods for preparing cerium-zirconium solid solutions, and is to convert soluble components into insoluble compounds by using a precipitant, and then obtain corresponding compounds through the procedures of separation, washing, drying, roasting and the like. The precipitate obtained in the coprecipitation method is hydroxide or salt of cerium and zirconium, and needs to undergo a high-temperature solid-phase reaction stage to form a solid solution, and the high temperature can cause the reduction of the specific surface area; in addition, the obtained precipitate exists in water, and ions are aggregated and grown under the action of surface tension in the drying process.
The combination of coprecipitation and hydrothermal method overcomes the defects of coprecipitation technology, and becomes a hot research direction for synthesizing high-performance cerium-zirconium solid solution at present, and the prior art has proved that the cerium-zirconium composite oxide material with large specific surface area can be prepared and obtained, and the material forms a stable crystalline phase structure at a lower roasting temperature, and can be used for catalytic combustion of methane (reference documents: Longqin et al, preparation of cerium-zirconium composite oxide and characterization of catalytic activity of methane combustion [ J ] Chinese non-ferrous metal academic report 2006,16(6): 1076-1080.).
However, in the prior art, it has not been possible to investigate whether the influence on the crystal phase structure and the high-temperature stability of the cerium-zirconium composite oxide with a specific composition exists by adjusting the preparation conditions or the process of the coprecipitation-hydrothermal combined method. CN110026177A provides a method for preparing a cerium-zirconium solid solution by adopting coprecipitation-hydrothermal combination, and the cerium-zirconium solid solution with better ageing resistance is obtained by adjusting the concentration of metal oxide in the primary mixture, but the reduction performance is poorer. CN106732521A adds ammonia water into the raw material by two-fluid spray feeding, the obtained cerium-zirconium solid solution has better oxygen storage performance, but the performance difference before and after aging is obvious.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a cerium-zirconium composite oxide having uniform particle size distribution, excellent hydrogen reduction performance, and stable structure at high temperature without agglomeration, which is prepared by an optimized co-precipitation-hydrothermal coupling method.
In one aspect, the present invention provides a method for preparing a cerium-zirconium composite oxide with a stable high-temperature structure, comprising: dissolving and mixing a cerium source, a zirconium source and at least one rare earth metal source except cerium to obtain an acidic mixed solution, adjusting the pH of the acidic mixed solution to 3-6, carrying out coprecipitation reaction with an alkaline precipitator, carrying out hydrothermal reaction, and carrying out high-temperature heat treatment on the obtained product to obtain the cerium-based cerium-doped cerium oxide.
Further, the pH of the acidic mixed solution is adjusted to 3 to 5, preferably 4 to 5.
Wherein the dissolution is preferably in water; the heat treatment may be calcination.
In the earlier work of the applicant, it was found that, because the initial pH of the acidic mixed solution is about 0.05 when the acidic mixed solution is prepared, the ion freeness of the solution is high, if the acidic mixed solution is directly added into an alkaline precipitant for precipitation, the ions in the solution or solid solution phase separation is caused due to inconsistent precipitation rates, and if the pH reaches a certain alkalinity after precipitation, and then the cerium-zirconium metal ions are completely reacted to generate corresponding hydroxides after hydrothermal treatment. However, the applicant found in later work that the level of alkalinity after precipitation has an effect on the uniformity and stability of the crystal phase structure, and the crystal grains of the synthesized cerium-zirconium solid solution increase with the increase of the pH of the solution after precipitation, which may be caused by that the nucleation rate and the growth rate of the hydroxide increase under alkaline conditions with the increase of the pH of the solution system after precipitation, but the growth rate is greater than the nucleation rate, so that the crystal grains of the formed cerium-zirconium solid solution are larger. Therefore, the preparation method provided by the application can synthesize the cerium-zirconium solid solution with more uniform crystal phase structure by adjusting the precipitation process of the coprecipitation-hydrothermal combined method. Experiments show that the cerium-zirconium composite oxide obtained by the preparation method provided by the application has good hydrogen reduction performance and excellent high-temperature structural stability, and also shows more remarkable low-temperature catalytic purification activity.
Further, in the method, the pH of the acidic mixed solution is adjusted by using an alkaline precipitator. Preferably, the pH of the acidic mixed solution is adjusted using aqueous ammonia under a water bath condition at 50 ℃.
Further, the conditions of the coprecipitation reaction are as follows: adding the acidic mixed solution into the excessive alkaline precipitator, and stirring the mixture to react for at least 30 minutes.
Further, the alkaline precipitant is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide and organic amine, preferably ammonia water, and more preferably ammonia water with the concentration of 10-15 mol/L. More preferably, the acidic mixed solution is transferred to ammonia water within 40min under stirring, and stirring is continued for 30min after the transfer is completed.
Further, the hydrothermal reaction conditions are as follows: hydrothermal reaction is carried out for 18-24h at 160-200 ℃, preferably the hydrothermal reaction is carried out in a high-pressure reaction kettle, and more preferably the hydrothermal reaction is carried out for 20h at 180 ℃ under the condition of the rotating speed of 200 r/min. In one embodiment, the hydrothermal slurry is filter-pressed, washed with deionized water and lauric acid, the suction-filtered organic matter is recovered, and the washed filter cake is calcined.
Further, the conditions of the high-temperature heat treatment are as follows: calcining at 700-900 deg.C for 4-8h, preferably at 750 deg.C for 4h, wherein the furnace gas flow is controlled at 10-20L (air)/min/kg.
Further, the cerium source, the zirconium source and the source of the rare earth metal other than cerium are respectively selected from one or more of nitrate, sulfate, carbonate, acetate and chloride of cerium, zirconium and the rare earth metal other than cerium, and nitrate is preferred.
In one embodiment, the cerium source may be one or more of cerium ammonium nitrate, cerium chloride, cerium sulfate, cerium carbonate; the zirconium source can be one or more of zirconium nitrate, zirconyl nitrate, zirconium carbonate, zirconium oxychloride, zirconium sulfate, zirconium acetate and zirconyl acetate; the rare earth metal other than cerium may be one or more of lanthanum (La), yttrium (Y), praseodymium (Pr), neodymium (Nd), scandium (Sc), samarium (Sm) and gadolinium (Gd), and preferably La, Y, Pr and Nd.
In a preferred embodiment, the preparation raw material may be zirconium nitrate, ammonium ceric nitrate, lanthanum nitrate, praseodymium nitrate, wherein the praseodymium nitrate may be prepared by dissolving praseodymium oxide in concentrated nitric acid.
On the other hand, the invention also provides the cerium-zirconium composite oxide prepared by the method, which comprises cerium oxide, zirconium oxide and at least one rare earth metal oxide except cerium, wherein the hydrogen temperature programming reduction temperature of the cerium-zirconium composite oxide is lower than 550 ℃.
Further, the rare earth metal oxide other than cerium is selected from one or more of lanthanum oxide, praseodymium oxide, yttrium oxide and neodymium oxide, and lanthanum oxide and praseodymium oxide are preferred.
Further, the cerium-zirconium composite oxide comprises 35-45 wt% of cerium oxide, 45-55 wt% of zirconium oxide, 5-10 wt% of lanthanum oxide and 5-10 wt% of praseodymium oxide; preferably, the cerium-zirconium composite oxide includes 40 wt% of cerium oxide, 50 wt% of zirconium oxide, 5 wt% of lanthanum oxide, and 5 wt% of praseodymium oxide.
Further, the cerium oxide, zirconium oxide, lanthanum oxide and praseodymium oxide may be respectively represented by CeO2、ZrO2、La2O3、Pr6O11Is provided in the form of (1).
On the other hand, the invention also provides the cerium-zirconium composite oxide in the preparation of the gas low-temperature catalystThe application comprises the carbon oxides, the nitrogen oxides and the hydrocarbon gas, preferably, the gas is tail gas containing CO and NOXAnd C2H6Etc.; the low temperature is a temperature not exceeding 250 ℃, and preferably, the low temperature is not exceeding 230 ℃.
Further, the cerium-zirconium composite oxide is also supported with 0.1 to 5 wt% of a noble metal, preferably, the supported amount of the noble metal is 0.5 to 2 wt%, more preferably 0.5 wt%. The noble metal can be gold, platinum, palladium, rhodium, and is preferably palladium.
In the present application, the hydrogen reducing ability of the cerium-zirconium composite oxide is represented by H2-TPR measurement. The Temperature Programmed Reduction (TPR) method is one of the temperature programmed analytical methods, in the TPR experiment, a certain amount of metal oxide catalyst is placed in a fixed bed reactor, reducing gas flow passes through the catalyst at a certain flow rate, while the catalyst is linearly heated at a certain rate, and when the temperature reaches a certain value, the oxide on the catalyst starts to be reduced: MO(s) + H2(g)＝M(s)+H2O (g), H after passing through the catalyst bed due to the inconvenience of reducing gas flow rate2Change of concentration and recording H with recorder2The change curve of the concentration along with the temperature is the TPR spectrum of the catalyst, which is a peak-shaped curve, each TPR peak in the graph generally represents a reducible species in the catalyst, the temperature corresponding to the maximum value of the TPR peak is called as the peak Temperature (TM), the height of the TM reflects the difficulty degree of the reduction of the oxidized species on the catalyst, and the area size contained under the peak-shaped curve is in direct proportion to the amount of the oxide. The TPR is studied on a supported or unsupported metal or metal oxide catalyst (in the case of a metal catalyst, a metal oxide is obtained by oxidation treatment). The information such as the valence state change of the metal, the interaction between two metals, the interaction between the metal oxide and the carrier, the activation energy of the reduction reaction of the oxide and the like can be obtained through a TPR experiment.
Experiments show that the cerium-zirconium composite oxide prepared by the preparation method provided by the application has T to CO when the cerium-zirconium composite oxide is freshly prepared (calcined at 750 ℃ for 4 hours)50As low as 151 ℃ and T90Low to 173 ℃ for NO2T of50Down to 154 ℃ and T90As low as 183 ℃ for C2H6T of50As low as 195 ℃ and T90As low as 224 ℃; t for CO after its ageing (4 h at 1100 ℃ C.)50As low as 165 ℃ and T90Down to 176 ℃ for NO2T of50As low as 162 ℃ and T90As low as 194 ℃ for C2H6T of50Down to 207 ℃ and T90As low as 232 deg.c and catalytic conversion temperature before and after ageing lower than 20 deg.c. Therefore, the cerium-zirconium composite oxide provided by the application has more remarkable low-temperature catalytic activity, the catalytic conversion temperature difference before and after aging is smaller, the high-temperature structure is stable, and the crystal phase structure characterization before and after aging can also show the result.
The invention has the beneficial effects that:
the preparation method of the cerium-zirconium composite oxide provided by the invention has the advantages of simple process, low cost and easy industrialization. The cerium-zirconium composite oxide prepared by the preparation method has better low-temperature catalytic activity and obvious high-temperature structural stability, has high utilization rate of noble metals, and is suitable for industrial production. Experiments show that when 0.5 wt% of noble metal is loaded on the newly prepared cerium-zirconium composite oxide, the oxide can react with CO and NO before and after aging2And C2H6T of50、T90The phase difference is less than 20 ℃.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is X-ray diffraction (XRD) graphs of a cerium-zirconium composite oxide obtained in example 2 before aging (curve ①) and after aging (curve ②), respectively;
fig. 2 is an X-ray diffraction (XRD) graphs of the cerium-zirconium composite oxide prepared in comparative example 1 before aging (curve ①) and after aging (curve ②), respectively.
Detailed Description
In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art, that the present application may be practiced without one or more of these specific details. In other instances, well-known features of the art have not been described in order to avoid obscuring the present application.
In the following examples, raw materials for preparing cerium-zirconium composite oxides were commercially available, unless otherwise specified. In the following examples, the vessel used in the hydrothermal reaction was a titanium autoclave with a volume specification of 10L, which was provided by special chemical equipment limited on the fume bench side; the analysis of the reduction temperature of the cerium-zirconium solid solution was carried out by using a PCA1200-TPR instrument from Pioded; the gas composition analysis was performed using an infrared flue gas analyzer model HN-CK21 provided by Taiyuan Hainan instruments and meters Co.
The following examples provide a preparation method of a cerium-zirconium composite oxide, which specifically comprises the following steps:
s1, respectively dissolving and mixing a cerium source, a zirconium source and a rare earth metal source except cerium to obtain an acidic mixed solution;
s2, adjusting the pH value of the acid mixed solution to 3-6;
s3, taking excessive strong ammonia water, slowly adding the acidic mixed solution with the pH adjusted in the step S2, and stirring for reacting for a period of time to obtain reaction slurry;
s4, introducing the reaction slurry into a high-pressure reaction kettle, and carrying out high-temperature hydrothermal hydrolysis reaction for 18-24h at 180-220 ℃;
s5, pumping and filtering, pulping and washing, drying the filter cake at 120 ℃ for 10h, and calcining at 700-800 ℃ for 4-8h to obtain the cerium-zirconium composite oxide.
The following examples were prepared using the above-described method.
Example 1
Embodiment 1 provides a preparation method of a cerium-zirconium composite oxide, including the steps of:
1029.5g of zirconium nitrate is weighed, 2000ml of deionized water is used for dissolving until the solution is clear, 32.5g of praseodymium oxide is weighed, 67.5g of concentrated nitric acid is used for dissolving until the solution is clear, and the two solutions are combined to obtain solution A; 84.9g of lanthanum nitrate and 808.2g of ammonium ceric nitrate are weighed, added into the solution A and stirred until the solution is clear. Then, the pH of the solution A was adjusted to 3.0 with ammonia water under a water bath condition of 50 ℃ and finally the solution was made to 3500 ml.
800ml of ammonia water with the concentration of 12.8mol/l is measured, the volume is determined to 3500ml, and then the solution is transferred to a big white barrel. Transferring the solution A into the ammonia water within 40min under stirring, and continuously stirring for reacting for 30min after the transfer is finished, wherein the slurry after the reaction is B.
Transferring the slurry B into a 10L titanium kettle, and carrying out hydrothermal treatment at 180 ℃ for 20h under the condition of the rotating speed of 200 r/min. The slurry after hydrothermal treatment was press-filtered, washed 3 times with 50L of deionized water, 2 times with 560g of lauric acid, and the organic matter obtained by suction filtration was recovered. Calcining the washed filter cake at 750 ℃ for 4 h; the flow rate of the furnace body gas is controlled at 10-20L (air)/min/kg (oxide). The calcined material is sieved by a 200-250 mesh sieve to obtain the final product.
The cerium-zirconium composite oxide prepared by the method comprises the following components: CeO (CeO)240％，ZrO 250％，La2O35％，Pr6O115 percent. Wherein the concentration of the oxide is 80g/L, and the total mass of the oxide is 650 g.
Example 2
1029.5g of zirconium nitrate is weighed and dissolved by 2000ml of deionized water until the solution is clear, 32.5g of praseodymium oxide is weighed and dissolved by 67.5g of concentrated nitric acid until the solution is clear, and the two solutions are combined to obtain solution A. 84.9g of lanthanum nitrate and 808.2g of ammonium ceric nitrate are weighed, added into the solution A and stirred until the solution is clear. Then, the pH of the solution A was adjusted to 4.0 with ammonia water under a water bath condition of 50 ℃ and finally the solution was made to 3500 ml.
800ml of ammonia water with the concentration of 12.8mol/l is measured, the volume is determined to 3500ml, and then the solution is transferred to a big white barrel. Transferring the solution A into ammonia water within 40min under stirring, and continuously stirring to react for 30min after the transfer is finished, wherein the slurry after the reaction is B.
Transferring the slurry B into a 10L titanium kettle, and carrying out hydrothermal treatment at 180 ℃ for 20h under the condition of the rotating speed of 200 r/min. The slurry after hydrothermal treatment was press-filtered, washed 3 times with 50L of deionized water, 2 times with 560g of lauric acid, and the organic matter obtained by suction filtration was recovered. Calcining the washed filter cake at 750 ℃ for 4 h; the flow rate of the furnace body gas is controlled at 10-20L (air)/min/kg (oxide). The calcined material is sieved by a 200-250 mesh sieve to obtain the final product.
The cerium-zirconium composite oxide prepared by the method comprises the following components: CeO (CeO)240％，ZrO 250％，La2O35％，Pr6O115 percent. Wherein the concentration of the oxide is 80g/L, and the total mass of the oxide is 650 g.
Example 3
Embodiment 3 provides a preparation method of a cerium-zirconium composite oxide, including the steps of:
1029.5g of zirconium nitrate is weighed and dissolved by 2000ml of deionized water until the solution is clear, 32.5g of praseodymium oxide is weighed and dissolved by 67.5g of concentrated nitric acid until the solution is clear, and the two solutions are combined to obtain solution A. 84.9g of lanthanum nitrate and 808.2g of ammonium ceric nitrate are weighed, added into the solution A and stirred until the solution is clear. Then, the pH of the solution A was adjusted to 5.0 with ammonia water under a water bath condition of 50 ℃ and finally the solution was made to 3500 ml.
800ml of ammonia water with the concentration of 12.8mol/l is measured, the volume is determined to 3500ml, and then the solution is transferred to a big white barrel. Transferring the solution A into ammonia water within 40min under stirring, and continuously stirring to react for 30min after the transfer is finished, wherein the slurry after the reaction is B.
Transferring the slurry B into a 10L titanium kettle, and carrying out hydrothermal treatment at 180 ℃ for 20h under the condition of the rotating speed of 200 r/min. The slurry after hydrothermal treatment was press-filtered, washed 3 times with 50L of deionized water, 2 times with 560g of lauric acid, and the organic matter obtained by suction filtration was recovered. Calcining the washed filter cake at 750 ℃ for 4 h; the flow rate of the furnace body gas is controlled at 10-20L (air)/min/kg (oxide). The calcined material is sieved by a 200-250 mesh sieve to obtain the final product.
Cerium prepared by the above methodA zirconium composite oxide comprising: CeO (CeO)240％，ZrO 250％，La2O35％，Pr6O115 percent. Wherein the concentration of the oxide is 80g/L, and the total mass of the oxide is 650 g.
Example 4
Embodiment 4 provides a preparation method of a cerium-zirconium composite oxide, including the steps of:
1029.5g of zirconium nitrate is weighed and dissolved by 2000ml of deionized water until the solution is clear, 32.5g of praseodymium oxide is weighed and dissolved by 67.5g of concentrated nitric acid until the solution is clear, and the two solutions are combined to obtain solution A. 84.9g of lanthanum nitrate and 808.2g of ammonium ceric nitrate are weighed, added into the solution A and stirred until the solution is clear. Then, the pH of the solution A was adjusted to 6.0 with ammonia water under a water bath condition of 50 ℃ and finally the solution was made to 3500 ml.
Measuring 800ml of ammonia water with the concentration of 12.8mol/L, fixing the volume to 3500ml, and transferring the solution to a big white barrel. Transferring the solution A into ammonia water within 40min under stirring, and continuing stirring for 30min after the transfer is finished, wherein the slurry after the reaction is B.
Transferring the slurry B into a 10L titanium kettle, and carrying out hydrothermal treatment at 180 ℃ for 20h under the condition of the rotating speed of 200 r/min. The slurry after hydrothermal treatment was press-filtered, washed 3 times with 50L of deionized water, 2 times with 560g of lauric acid, and the organic matter obtained by suction filtration was recovered. Calcining the washed filter cake at 750 ℃ for 4 h; the flow rate of the furnace body gas is controlled at 10-20L (air)/min/kg (oxide). The calcined material is sieved by a 200-250 mesh sieve to obtain the final product.
The cerium-zirconium composite oxide prepared by the method comprises the following components: CeO (CeO)240％，ZrO 250％，La2O35％，Pr6O115 percent. Wherein the concentration of the oxide is 80g/L, and the total mass of the oxide is 650 g.
Comparative example 1
Comparative example 1 was prepared in substantially the same manner as examples 1-4, except that the pH of the acidic mixture prior to the coprecipitation reaction was varied as follows:
1029.5g of zirconium nitrate is weighed and dissolved by 2000ml of deionized water until the solution is clear, 32.5g of praseodymium oxide is weighed and dissolved by 67.5g of concentrated nitric acid until the solution is clear, and the two solutions are combined to obtain solution A. 84.9g of lanthanum nitrate and 808.2g of ammonium ceric nitrate are weighed, added into the solution A and stirred until the solution is clear. Then, the pH of the solution A was adjusted to 1.0 with ammonia water under a water bath condition of 50 ℃ and finally the solution was made to 3500 ml.
Measuring 800ml of ammonia water with the concentration of 12.8mol/L, fixing the volume to 3500ml, and transferring the solution to a big white barrel. Transferring the solution A into ammonia water within 40min under stirring, and continuing stirring for 30min after the transfer is finished, wherein the slurry after the reaction is B.
Transferring the slurry B into a 10L titanium kettle, and carrying out hydrothermal treatment at 180 ℃ for 20h under the condition of the rotating speed of 200 r/min. The slurry after hydrothermal treatment was press-filtered, washed 3 times with 50L of deionized water, 2 times with 560g of lauric acid, and the organic matter obtained by suction filtration was recovered. Calcining the washed filter cake at 750 ℃ for 4 h; the flow rate of the furnace body gas is controlled at 10-20L (air)/min/kg (oxide). The calcined material is sieved by a 200-250 mesh sieve to obtain the final product.
The cerium-zirconium composite oxide prepared by the method comprises the following components: CeO (CeO)240％，ZrO 250％，La2O35％，Pr6O115 percent. Wherein the concentration of the oxide is 80g/L, and the total mass of the oxide is 650 g.
Evaluation of application Performance:
first, structural characterization
The XRD characterization before and after aging was performed on the cerium-zirconium composite oxide obtained in each of the above examples, wherein XRD graphs before and after aging of example 2 are shown in fig. 1, XRD graphs before and after aging of comparative example 1 are shown in fig. 2, and heat treatment conditions of a freshly prepared sample before aging, i.e., calcination at 750 ℃ for 4 hours and calcination at 1100 ℃ for aging for 4 hours, were performed, respectively.
The cerium-zirconium composite oxides obtained in the above examples were subjected to hydrogen temperature programmed reduction (H)2TPR) by the following method: placing about 0.1g of catalyst in a U-shaped quartz tube reactor, introducing He, heating to 400 deg.C, holding for 2 hr, removing gas adsorbed on the surface of the catalyst, cooling to 50 deg.C, and switching gas to 10% H2-He mixed gas, ring at gas flow rate of 30ml/minTreating for 2 hours under the environment, purging under He for 30min, after the system is stabilized, raising the temperature to 800-900 ℃ at the speed of 15 ℃/min, and detecting a hydrogen signal by using a thermal conductivity cell detector (TCD). Measured H2The TPR temperature is used to characterize the redox performance of the resulting catalyst, with lower temperatures indicating better reduction performance. The results before and after aging for each example are shown in table 1.
Table 1 examples H before and after aging2TPR temperature
| Examples of the invention | Fresh sample (750 ℃ -4H) H2TPR temperature/. degree.C | Aged sample (1100 ℃ -4H) H2TPR temperature/. degree.C |
| Example 1 | 495 | 572 |
| Example 2 | 522 | 608 |
| Example 3 | 541 | 622 |
| Example 4 | 530 | 614 |
| Comparative example 1 | 586 | 723 |
As can be seen from table 1, the cerium-zirconium composite oxide prepared by the method has a lower reduction temperature before and after aging, while the cerium-zirconium composite oxide obtained in comparative example 1 has a higher reduction temperature, which is not favorable for its catalytic activity at high temperature. Further, as can be seen from the XRD graphs before and after aging of example 2, the cerium-zirconium composite oxide prepared by the method described in example maintains a stable solid solution structure after high-temperature aging at 1100 deg.C, whereas the product prepared in comparative example 1 begins to show segregation, ZrO, after high-temperature aging at 1100 deg.C2And precipitated from solid solution.
II, testing catalytic activity
A noble metal was supported on the cerium-zirconium composite oxides prepared in examples 1 to 4 and comparative example 1 (heat treatment temperature 750 ℃) as carriers to conduct a catalytic activity evaluation experiment, wherein the catalyst was prepared by a conventional equivalent-volume impregnation method using Rh (NO) as a carrier3)3·2H2O is a precursor of the noble metal solution. The theoretical loading of the noble metal is 0.5 wt%, and the catalyst slurry loaded with the metal is dried in a rotary evaporator, then is dried in a forced air drying oven at 110 ℃ for 3 hours, and is calcined in a calcining furnace in an air atmosphere at 500 ℃ for 3 hours.
The catalytic activity tests of the cerium-zirconium composite oxide loaded with noble metal during fresh preparation and after aging are respectively carried out, and the test method comprises the following steps: simulation gas: NO2-C2H6-CO-O2(4 kinds of mixed gas are mixed before entering a catalyst bed layer), the balance gas is Ar, and the volume space velocity is 30000h-1(ii) a Results of the experiment are expressed as T50、T90To measure the catalytic activity, T, of the catalyst50The reaction temperature at 50% conversion of the reactants, T90Is the reaction temperature at which the conversion of the reactants is 90%, where T50And T90The lower the content, the better the catalytic effect.
Table 2 shows the catalytic activity when freshly prepared (750 ℃ to 4h)
Table 3 illustrates the catalytic activity after aging (1100 ℃ C. -4h)
As is clear from tables 2 to 3, the composition of the alloy was 40% CeO2、50％ZrO2、5％La2O3、5％Pr6O11The cerium-zirconium composite oxide prepared by the methods of examples 1 to 4 and loaded with noble metal has a significantly higher low-temperature catalytic activity than that of comparative example 1, and the cerium-zirconium composite oxide prepared in examples 1 to 4 has a significantly higher T value before and after high-temperature aging50And T90The difference is only about 10 ℃, excellent high-temperature structural stability is shown, and the low-temperature catalytic effect of the comparative example 1 after high-temperature aging is obviously reduced.
Further, from the above results, it can be also seen that the pH of the acidic mixed solution before the coprecipitation reaction is carried out has a large influence on the low-temperature catalytic activity of the cerium-zirconium composite oxide of the same composition, and that there is a large difference between the low-temperature catalytic effects of the respective examples, particularly, when the pH before the coprecipitation reaction is increased from 3 to 6, the catalytic effect tends to increase first and then decrease. Particularly, when the pH value of the acid mixed solution is 4-5, the low-temperature catalytic effect of the obtained cerium-zirconium composite oxide reaches the optimal value.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A preparation method of a cerium-zirconium composite oxide with high-temperature structure stability is characterized by comprising the following steps:
dissolving and mixing a cerium source, a zirconium source and at least one rare earth metal source except cerium to obtain an acidic mixed solution, adjusting the pH of the acidic mixed solution to 3-6, carrying out coprecipitation reaction with an alkaline precipitator, carrying out hydrothermal reaction, and carrying out high-temperature heat treatment on the obtained product to obtain the cerium-based cerium-doped cerium oxide.
2. The method according to claim 1, wherein the pH of the acidic mixed solution is adjusted to 3 to 5, preferably to 4 to 5.
3. The method of claim 1, wherein the pH of the acidic mixed solution is adjusted using an alkaline precipitant.
4. The method according to claim 1, wherein the conditions of the coprecipitation reaction are: adding the acidic mixed solution into the excessive alkaline precipitator, and stirring for reaction for at least 30 minutes; or the conditions of the hydrothermal reaction are as follows: carrying out hydrothermal reaction at 160-200 ℃ for 18-24 h; or the conditions of the high-temperature heat treatment are as follows: calcining at 700-900 deg.c for 4-8 hr.
5. The method according to any one of claims 1 to 4, wherein the alkaline precipitant is selected from one or more of ammonia, sodium hydroxide, potassium hydroxide, and organic amines, preferably ammonia.
6. The process according to claim 1, characterized in that the cerium source, the zirconium source and the source of the rare earth metal other than cerium are respectively selected from one or more of the nitrates, sulfates, carbonates, acetates, chlorides of cerium, zirconium and of the rare earth metal other than cerium, preferably nitrates.
7. The cerium-zirconium composite oxide according to any one of claims 1 to 6, comprising a cerium oxide, a zirconium oxide and at least one rare earth metal oxide other than cerium, wherein the cerium-zirconium composite oxide has a hydrogen temperature programmed reduction temperature of less than 550 ℃.
8. The cerium-zirconium composite oxide according to claim 7, wherein the oxide of a rare earth metal element other than cerium is one or more selected from lanthanum oxide and praseodymium oxide.
9. The cerium-zirconium composite oxide according to claim 7, wherein the cerium-zirconium composite oxide comprises 35 to 45 wt% cerium oxide, 45 to 55 wt% zirconium oxide, 5 to 10 wt% lanthanum oxide, 5 to 10 wt% praseodymium oxide; preferably, the cerium-zirconium composite oxide includes 40 wt% of cerium oxide, 50 wt% of zirconium oxide, 5 wt% of lanthanum oxide, and 5 wt% of praseodymium oxide.
10. Use of the cerium zirconium composite oxide according to claim 7 for the preparation of low temperature catalysts for gases comprising carbon oxides, nitrogen oxides and hydrocarbon gases; the low temperature is a temperature not exceeding 250 ℃; preferably, the cerium-zirconium composite oxide is further supported with 0.1 to 5 wt% of a noble metal; more preferably, the noble metal is rhodium.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111939905A (en) * | 2020-08-26 | 2020-11-17 | 湖南第一师范学院 | Preparation method of catalyst for automobile exhaust, product and application thereof |
| CN113371756A (en) * | 2021-07-13 | 2021-09-10 | 河南工业大学 | La-Sc-ZrO2 nano-crystal material and preparation method thereof |
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| WO2023095839A1 (en) * | 2021-11-29 | 2023-06-01 | 東ソー株式会社 | Powder and production method therefor |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130336864A1 (en) * | 2012-06-15 | 2013-12-19 | Basf Corporation | Composites Of Mixed Metal Oxides For Oxygen Storage |
| CN110026176A (en) * | 2019-04-22 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide, preparation method and application |
| CN110026175A (en) * | 2019-04-17 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide and its application in catalysis CO oxidation reaction |
| CN110026177A (en) * | 2019-04-22 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium sosoloid, preparation method and application |
| CN110252275A (en) * | 2019-05-21 | 2019-09-20 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide of high-specific surface area and its preparation method and application |
-
2019
- 2019-10-12 CN CN201910968467.8A patent/CN110841623A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130336864A1 (en) * | 2012-06-15 | 2013-12-19 | Basf Corporation | Composites Of Mixed Metal Oxides For Oxygen Storage |
| CN110026175A (en) * | 2019-04-17 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide and its application in catalysis CO oxidation reaction |
| CN110026176A (en) * | 2019-04-22 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide, preparation method and application |
| CN110026177A (en) * | 2019-04-22 | 2019-07-19 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium sosoloid, preparation method and application |
| CN110252275A (en) * | 2019-05-21 | 2019-09-20 | 山东国瓷功能材料股份有限公司 | A kind of cerium zirconium compound oxide of high-specific surface area and its preparation method and application |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111939905A (en) * | 2020-08-26 | 2020-11-17 | 湖南第一师范学院 | Preparation method of catalyst for automobile exhaust, product and application thereof |
| CN111939905B (en) * | 2020-08-26 | 2021-05-07 | 湖南第一师范学院 | Preparation method of catalyst for automobile exhaust, product and application thereof |
| CN113371756A (en) * | 2021-07-13 | 2021-09-10 | 河南工业大学 | La-Sc-ZrO2 nano-crystal material and preparation method thereof |
| WO2023095839A1 (en) * | 2021-11-29 | 2023-06-01 | 東ソー株式会社 | Powder and production method therefor |
| JP7472956B2 (en) | 2021-11-29 | 2024-04-23 | 東ソー株式会社 | Powder and its manufacturing method |
| CN114570423A (en) * | 2021-12-27 | 2022-06-03 | 中国科学院山西煤炭化学研究所 | Catalyst for preparing ethanol and propanol from synthesis gas and preparation method and application thereof |
| CN114570423B (en) * | 2021-12-27 | 2023-09-15 | 中国科学院山西煤炭化学研究所 | Catalyst for preparing ethanol and propanol from synthesis gas, and preparation method and application thereof |
| CN115301224A (en) * | 2022-08-18 | 2022-11-08 | 中国科学院赣江创新研究院 | Cerium-zirconium based environmental catalyst with self-protection thermal stability and preparation method and application thereof |
| CN115301224B (en) * | 2022-08-18 | 2023-11-14 | 中国科学院赣江创新研究院 | Cerium-zirconium-based environment catalyst with self-protection thermal stability and preparation method and application thereof |
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